1. Field of the Invention
The present invention relates to a pump for feeding a cooling fluid for an internal combustion engine of a motor vehicle in which a feed quantity is controlled as a function of engine operating parameters or for feeding a cleaning fluid for headlamps or shields of a motor vehicle, the pump including a temperature sensor for regulating the quantity of fluid fed by the pump.
2. Description of the Related Art
Pumps having a temperature sensor are often used in motor vehicles when the feed quantity required is dependent on the temperature. Every motor vehicle has, for example, a pump for feeding the cooling fluid. The pump is coupled fixedly to the internal combustion engine via V-belts so that the rotational speed of the pump is correspondingly coupled to the rotational speed of the internal combustion engine and fluctuates as the speed of the internal combustion engine changes. However, since the amount of heat from the internal combustion engine to be discharged by the cooling fluid varies, the cooling fluid quantity supplied to the internal combustion engine is regulated by at least one valve arranged in the cooling circuit and regulated by a temperature sensor.
In cleaning systems for headlamps or shields, the cleaning capacity of the fluid increases as the temperature of the cleaning fluid increases. Accordingly, the optimum fluid quantity presupposes that the temperature is detected as accurately as possible.
According to the prior art, a temperature sensor is inserted into a line element of the fluid circuit to detect the temperature. The measurement values obtained by this sensor are then recorded in a central control unit and evaluated to activate the pump.
A problem with the prior art devices is that the detection of the temperature is carried out often only with an unsatisfactory degree of accuracy. A complicating effect is that the exact position of the temperature detector in the line system must be known to account for adjacent heat sources and heat sinks which may influence the measurement values. Consequently, each different motor vehicle type or motor vehicle variations must take into account correction values in the activation of the pump. These correction values must be filed in a storage element. The outlay for activating such a pump is therefore comparatively high.
It is an object of the present invention to design a pump having a temperature sensor in such a way that the cooling fluid quantity can be regulated as exactly as possible for different applications and conditions of installation.
The object according to the present invention is met in that the pump and the temperature sensor are designed as an integral structural unit. By virtue of the temperature sensor being integrated according to the invention into the pump, the structural unit according to the invention is particularly cost-effective to produce and is simultaneously simple to mount in a motor vehicle. The association between the temperature sensor and the pump is determined directly so that the activation of the pump is simplified and an additional outlay for contact between the two components is avoided. Furthermore, the risk of incorrect mounting and the susceptibility to operating faults are markedly reduced.
According to an embodiment of the present invention, the pump may be used as a cooling fluid pump for the internal combustion engine of a motor vehicle. The pump according to this embodiment has an electric motor connected for driving the pump. The rotational speed of the electric motor is controlled as a function of signals from the temperature sensor. Accordingly, the temperature of the cooling fluid directly accounted for in the regulation of the feed volume, without the possibility of falsifications of measurement values due to a lengthy distance of the temperature sensor from the pump. The pump according to the present invention optimally adapts the feed volume to the respective cooling requirement. In contrast to cooling fluid pumps which are driven directly by the internal combustion engine via V-belts, the energy requirement of the pump is lower, because it always operates at the exact feed capacity required.
It is particularly beneficial embodiment of the present invention, the temperature sensor is connected on the outside of a pump casing of the pump. The arrangement of the temperature sensor on the pump casing at the same time allows a reliable detection of the temperature to be determined through the wall of the pump casing and easy exchange of the temperature sensor in the event of a fault. Since the temperature sensor is not in direct contact with the liquid to be fed, the pump may be used without difficulty with aggressive fluids.
In a further embodiment of the pump according to the present invention, the pump casing has a reduced wall thickness in the region of the temperature sensor. The transition of the heat given off by the fluid through the wall of the pump casing is thereby improved substantially so that the accuracy of the measurement values detected in this way is appreciably increased. Furthermore, the response behavior in the event of pronounced temperature fluctuations, in particular when the motor vehicle is being started up, is also improved. The improved heat transition may be additionally increased by an appropriate selection of a suitable pump casing material.
The pump casing may be provided with an outer flattened portion or else with a shaped-out portion arranged on an inner wall to achieve the reduced wall thickness at the intended position of the temperature sensor. Alternatively, the pump may include a recess in which the temperature sensor is inserted. In this alternative embodiment, the temperature sensor is separated from the fluid only by a comparatively small remaining material thickness of the wall of the pump casing. Therefore, heat losses such as those due to discharge via the surface of the pump casing are considerably restricted. At the same time, the recess allows the temperature sensor to be arranged so that it is effectively protected against damage. Accordingly, mechanical damage caused by adjacent components may be avoided.
A further benefit is achieved by arranging the temperature sensor in the region of a pump chamber of the pump. The temperature of the fluid may thereby be transmitted quickly and without additional heat conduction losses. For this purpose, the temperature sensor may be fixed, for example, on the outside to a wall of the pump chamber or else is inserted into a recess which allows direct contact between the fluid and the temperature sensor. At the same time, it is possible to have a combination of a temperature sensor designed both for determining the temperature of the fluid and for detecting the feed quantity, with the result that the outlay in terms of production is reduced and the mounting process is simplified.
In another embodiment of the present invention the temperature sensor is arranged in the region of a connecting flange of the pump. In this embodiment, the measurement values for determining the temperature of the fluid are detected directly before the fluid enters the pump chamber. This embodiment avoids possible measurement value deviations which may be caused by the pump drive transmitting extraneous heat to the fluid. The measurement values therefore have correspondingly increased accuracy.
In yet a further embodiment of the present invention, the temperature sensor may be arranged in the region of an inlet orifice of the pump chamber. This embodiment avoids possible measurement value deviations which may be caused by the pump drive transmitting extraneous heat to the fluid and additionally avoids any deviations which may arise due to heat possibly being dissipated in the connection region of a line element.
At the same time, a further-simplified embodiment of the pump according to the present invention is achieved in that the temperature sensor is combined jointly with a control of the pump in a structural unit. The temperature sensor, the essential parts of which consist of electric components, may thus be integrated expediently into the control of the pump. An additional outlay for contacting the temperature sensor is therefore avoided, and operating reliability is simultaneously increased. The temperature sensor may also be arranged, for example, on a pump circuit board common to the control, with the result that the outlay in terms of production may be reduced even further.
The temperature sensor may be connected to a carrier element produced from a ceramic material. The fixing of the temperature sensor can thereby be effected equally reliably and without the risk of damage to adjacent electric components which are therefore exposed to the heat to be detected. For this purpose, the carrier produced from the ceramic material at the same time allows good heat transmission, and the electric circuit elements can be applied in a simple way as a hybrid circuit and therefore require only a small amount of space. The insensitivity of the ceramic material to high temperatures also prevents mechanical damage to the carrier and consequently to the connection between the temperature sensor and the pump.
A development of the invention is also particularly useful in which a heat conduction compound is provided for improved heat transmission between the temperature sensor and the pump casing. This ensures an appreciably improved transfer of heat to the temperature sensor, in that the direct contact surface between the temperature sensor and the pump casing is supplemented by an additional contact surface via the heat conduction compound. Consequently, the release of the temperature sensor from the direct contact surface on the pump casing due to vehicle vibrations is avoided, so that the operating reliability may be increased appreciably as a result.
In yet a further embodiment of the present invention, the temperature sensor is connected to the pump casing by a silicone adhesive compound. A uniform transfer of heat from the temperature sensor by means of a comparatively large-area heat exchange surface is thereby obtained, with the result that local temperature differences can be compensated and a measurement value deviation prevented. At the same time, simple mounting of the temperature sensor is achieved by gluing the temperature sensor to the pump casing in a suitable position a silicone adhesive compound.
The temperature sensor may be designed as a thermistor with a positive or negative temperature coefficient. As a result, the determination of the temperature and consequently also of the pump feed quantity dependent on this may be achieved without an electronic control unit. The use of a thermistor thereby allows the pump to be used even under difficult circumstances, in which the pump is subjected to high stress such that the use of electronic circuit elements is ruled out. The electric resistance of the thermistor, which is changed due to the respective temperature, therefore directly influences the feed capacity of the pump operated electrically for this purpose.
In another embodiment of the present invention, the pump is equipped with an actuator for regulating the throughflow quantity of the fluid by the fluid temperature detected by the temperature sensor. As a result, when the temperature deviates from a desired value, the fluid may be diverted into another line system to bypass the heating or cooling circuit. The feed quantity of the pump may at the same time be both changed and kept unchanged, and the excess fluid quantity can be used for heating or cooling further components.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.